[linux-lvm] balooning/dynamic snapshots?

Tomasz Chmielewski mangoo at wpkg.org
Tue Nov 13 17:13:20 UTC 2007

Right now, one has to specify a snapshot size.

If the snapshot takes more space that one specified with -s (size), that 
snapshot is automatically dropped, and is no longer usable.

Sometimes, it is just not possible to know beforehand how much data will 
change, but on the other hand, specifying 100% snapshot size is not 
possible or hard to estimate.

Is it possible to make a "balooning", or dynamic LVM snapshot? That is, 
if the snapshot reaches its maximum, it will be automatically resized, 
provided we still have space on the medium.

Looking at lvm manuals, I didn't see such a feature, and the only 
possibility seems to be to create a userspace program which would check 
the status of the snapshots periodically, and resize them if needed - 
but this seems crude, and may not work sometimes (very loaded system, 
volumes with a lot of writes etc.).

Tomasz Chmielewski

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